How to get a popup/alert to save text/attribute info of polygon, marker and then save to json?

[TCPHaryana]

How to get a popup/alert to save text/attribute info of polygon, marker and then save to json?
I am using custom save button.
map.pm.Toolbar.createCustomControl({
name: 'StoreShapes',
title: 'Store all shapes',
block: 'custom',
className: 'custom-control-icon',
toggle: true,
afterClick: generateGeoJson(),
});